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*Subject*: Re: bug in IDL's hanning() window-generating function*From*: Harold Cline <harold(at)rsinc.com>*Date*: Fri, 03 Aug 2001 15:54:33 -0600*Newsgroups*: comp.lang.idl-pvwave*Organization*: Research Systems Incorporated*References*: <9k8dt6$fki$1@news.orst.edu>*Xref*: news.doit.wisc.edu comp.lang.idl-pvwave:26030

Just an FYI for everyone on this topic. ;-) Thanks, Harold Cline IDL Product Manager ------------------------------------------ RELEASE_NOTE for IDL5.5: HANNING: The formula to compute the Hanning window has been changed from 0.5 * (1-Cos(2*!Pi*k/(N-1))) to 0.5 * (1-Cos(2*!Pi*k/N)). Because of the change from 1/(N-1) to 1/N, the Hanning window will no longer appear symmetric in the time domain, but will give improved results for spectral estimation. Additional notes: When filters such as the Hanning are to be used as finite-impulse response (FIR) filtering in the time domain, it is useful to have the filter be symmetric, and go to zero at both ends. However, if you are filtering your time series in preparation for doing spectral analysis, the filter should not be symmetric, and should not go to zero at one of the endpoints. Thus, the new behavior of the HANNING function assumes it will be used for spectral analysis. Reference: Oppenheim & Schafer (Discrete-Time Signal Processing, 1999), p. 468-469.

**Follow-Ups**:**Re: bug in IDL's hanning() window-generating function***From:*bennetsc

**References**:**bug in IDL's hanning() window-generating function***From:*Scott Bennett

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